Bandsaw Blade Breakage
Errol Caldwell
tried 3 different sources of blades, thinking that I was purchasing blades
with poor welds. I have also tried different types of blades usually 3/8 3
or 4 tpi. I keep the tension as low as I can and also loosen the tension
after use. When the blades break it is always at the weld and they let go
with enough force that they get mangled inside the saw and are useless for
re-welding. I can often tell the blades are going to break from the
increasing tick tick tick the blades make as the weld strikes the ceramic
guides. I believe the guides are set properly as well. I use a piece of
paper to adjust the distance from the blade and keep the back guide about
1/16th distance from the blade. What could be the problem? Most of what I am
cutting is bowl and other woodturning blanks. Would too fast a speed be a
problem? The blade seems to track consistently so I don't think the wheels
are out of alignment. I am at a loss.
l.van...@rogers.com
My suspicion is first 3/8 wide blades are probably to narrow for what
you are sawing, I would also set my back of the blade closer to the
guide, like just from not rubbing to just touching, however I doubt
that that is the mayor cause of breaking, pushing and twisting a to
narrow blade is what I would suspect as the mayor reason.
Do you have blades with a extra wide set, assuming you are sawing wet
wood also, because a wider set blade would have less friction and heat
build up and the kerf being wider would also help in less twisting of
the blade when maneuvering the wood around.
Just my look at it, there might be some other thought on this.
http://homepage.mac.com/l.vanderloo/PhotoAlbum25.html
Have fun and take care
Leo Van Der Loo
robo hippy
I have the same saw. I use it for resawing, and cutting out bowl
blanks. I do the radius cuts on my smaller saw with a 1/2 inch blade.
On the Laguna, I have been running an 1 1/4 blade. I did have one that
broke, but it didn't break on the weld. I keep the tension up high. I
agree that the 3/8 blade may be too light duty for the saw, and there
are several thicknesses of blades available. I wouldn't attempt to cut
16 inches high with that small of a blade.
robo hippy
George
"robo hippy" <reed...@comcast.net> wrote in message
news:1139036814.2...@g44g2000cwa.googlegroups.com...
Of course, 3/8 is _not_ to small for the saw, and it's absolutely necessary
for smaller work anyway, so I wouldn't worry much about that. Apply
appropriate tension and it will do fine.
On the subject of tension, too loose can be as bad as too tight at breaking
welds. The blade might be compressing as it decelerates into the wood ,
putting bending stress on the weld. I go with the manufacturer on tension
suggestions, but a little more is better than a little less. Make sure the
blade's supported close to the top of the piece.
Now on to feed rate and thrust bearings. You set them close, and feed at a
rate that barely deflects the blade in to them? Low tension can be your
enemy here, as well. Think Duginskie calls it "beam strength" in his
excellent book. Here's where wider blades make a difference - feed rate.
Closely related to feed rate is feed stability. If you don't have the blank
stable and supported below, it can wobble on you. This puts stress on the
blade, of which the weld is still the weakest part, the same way low tension
and high friction can. Get a flat surface to bear against with your scrub
and block planes. A circle-cutting jig is great insurance as well, assuring
that side loads are minimized. Make one, try it, and you'll see how it
makes what they told you about sawing - you have to feed as you turn, not
feed then turn - a cinch.
There's also a difference in blades beyond TPI, where yours sound fine for
small rough work and 6" blank cutting. I prefer set to skip in the teeth,
especially for wet woods. Keeps the blade from binding by making a wider
kerf. Your 3/8 will bind less than a wider blade at the rear, and binding
is what exacerbates low tension problems and heats the band, so you're
probably in a tradeoff there.
One last thing that is perhaps just a fetish at my house is corrosion. If
I'm cutting acid woods I always try and back the blade up manually through a
WD40-soaked paper towel to clean it. The pits that acid can form not only
ruin the sharpness, which of course means it feeds harder which means you
have to push harder and the blade binds in the cut and ... it eats the weld
as well. Maybe even more, because the area is rough from being ground flush
anyway. At the least, you'll get some more good cuts by keeping the blade
clean, so I figure it's worth it.
Peter Hyde
"Errol Caldwell" <caldwel...@sympatico.ca> wrote:
Errol,
looks like you have some good advice from others but i would like to add
some thoughts.
Blades do break! How much usage are you getting from a blade?
3 different sources of blades doesn't tell us if it was 3 different
manufacturers.
I am not familiar with your saw so have to ask is the motor Laguna
supplied or was it bought separately. If not a Laguna motor is it the
right speed (RPM).
Before you install a new blade run your fingers over the weld and check
for any roughness or bumps. Remove with a Dremel or a slip stone before
installing.
Try changing the ceramic guides with cool blocks.
Make sure the guides are set behind the tooth gullet when the blade is
at maximum deflection.
Use Pam as a lubricant when the blade is in the wood.
Lastly get Mark Duginske's book.
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robo hippy
I am curious as to why you would recomend the cool blocks over the
ceramic blade guides. They both run cool, and I would think that the
creamic would outlast the cool blocks.
robo hippy
Errol Caldwell
a difference.
"George" <George@least> wrote in message
news:43e48...@newspeer2.tds.net...
Errol Caldwell
mostly bowl blanks and usually from green wood. I have tried furniture band,
swedish silicon and other blades from R&D Bandsaws - usually Viking I
believe. I like 3/8 because I can turn smaller radii if I need to. I have
also tried a local supplier who does a good job on the welds but I don't
know where he gets his bands. Also tried blades from Starrat from a supplier
in Halifax. I suspect my problem is too low tension and not setting the
guides directly above the work. Sometimes I leave them a bit high and that
will add to blade compression. The ceramic guides are supposed to be even
better than cool blocks. Thanks for the advice.
"Peter Hyde" <nopeter....@sympatico.ca> wrote in message
news:nopeter.hydespam-E5...@nr-tor01.bellnexxia.net...
Peter Hyde
"Errol Caldwell" <caldwel...@sympatico.ca> wrote:
> I have been geting no more than a few hours use from the blades. I cut
> mostly bowl blanks and usually from green wood. I have tried furniture band,
> swedish silicon and other blades from R&D Bandsaws - usually Viking I
> believe. I like 3/8 because I can turn smaller radii if I need to. I have
> also tried a local supplier who does a good job on the welds but I don't
> know where he gets his bands. Also tried blades from Starrat from a supplier
> in Halifax. I suspect my problem is too low tension and not setting the
> guides directly above the work. Sometimes I leave them a bit high and that
> will add to blade compression. The ceramic guides are supposed to be even
> better than cool blocks.
I am not familiar with any of the brands you mention except Starret We
use these at work on a 20" General and they take all sorts of abuse and
never break. This saw is used by 10 different people of varying skill
levels and none of them even think of changing a blade or even matching
a blade to the sort of work they are doing. Materials cut range from
aluminum to plexiglass, plywood, maple and pine.
Sometimes the harder guides like ceramic tend to case harden the blade
especially if there is unevenness in the weld or they are set too close.
As the case hardening occurs it causes the area around the weld to
become brittle and the constant bending around the wheels causes
failure. 3 wheel machines also tend to break welds because of the
smaller radii of the wheels.
If you take a coarse sharpening stone and gently round the back edge of
the blade with the saw running it helps when cutting tight radii. Lee
Valley sells a special stone for this.
I think the low tension is a factor and you should always bring the top
guides down to be almost in contact with the wood. Also do not forget to
correctly adjust the bottom guides when you change blades. Don't laugh I
see it all the time!
Good luck!
Peter Hyde
"robo hippy" <reed...@comcast.net> wrote:
See my second posting to Errol. I have a Rockwell 14" BS and tried
ceramic and roller bearing guides and noticed more broken blades. Went
back to cool blocks and no breakages. Also I now recycle the Starret
blades from work. I cut and silver solder them to fit my Rockwell and
then sharpen with a high speed rotary tool. Good enough for blank
cutting and general work. I also tuned the BS with Mark Duginske's help
and can re-saw veneers with a freshly sharpened recycled 1/2"blade.
George
> Sometimes the harder guides like ceramic tend to case harden the blade
> especially if there is unevenness in the weld or they are set too close.
> As the case hardening occurs it causes the area around the weld to
> become brittle and the constant bending around the wheels causes
> failure. 3 wheel machines also tend to break welds because of the
> smaller radii of the wheels.
The ceramics are so frictionless that there isn't a chance to build heat.
Unless someone's been roughening yours, and it'll take some real abrasive,
not going to be the problem.
Not to mention, they don't wear as the blade tries to wander out from the
center of the circle you're cutting. Wear on softer cool blocks in these
circumstances can allow twisting of the blade, with premature consequences
of breakage.
Peter Hyde
wrote:
In Errol's original posting he mentioned a tick tick tick sound from the
blade before it broke. This suggests to me that the welds were rough and
in fact the ceramics are behaving like hammers and that sets up a
hardening effect that makes the weld more brittle and it breaks. I would
not personally go back to ceramics. I had breakages when I used them and
really don't know why. So I went back to cool blocks because they worked
better for me. The General at work has mild steel guides that get really
badly scored but the blades don't break they get retired!
robo hippy
my blade. He said to make sure the thrust guides were set properly,
perfectly in line with the blade, and to make sure that you had the top
guides down close to the wood. If either or both of these conditions
exist, it will put stresses on the blade that can cause it to break.
When my blade broke, it was also making a ticking sound, but I figured
that was because the 1 1/4 inch blade was moving about 1/4 inch
foreward each time the blade came around to the broken spot. He found
several other breaks in the blade, so it was trashed. The ticking sound
only started when the blade began to break. There is no sound when it
runs now.
robo hippy
George
The General at work has mild steel guides that get really
> badly scored but the blades don't break they get retired!
So breakage obviously has nothing to do with guide heat buildup, as the
steel guides are the worst offenders in that department. Not to mention the
wood itself!
He did say that he paid strict attention to only one of the setup criteria,
that of clearance on the guides. It's the low tension and poor support
that's getting him.